Field of the Invention
The present invention relates to a caliper unit for a vehicle. More particularly, the present invention relates to a caliper unit for a vehicle to which a floating ramp structure is applied.
Description of Related Art
In general, a brake device as a damping device of a vehicle is a main device used to decelerate or stop a driving vehicle and a drum brake and a disk brake as a hydraulic brake have been used.
The disk brake is a device that presses a brake pad to a disk to stop a vehicle. Recently, a disk brake with excellent braking performance has been mainly used compared with the drum brake.
The disk brake includes a disk that integrally rotates with a wheel and a caliper unit. The caliper unit includes an operating lever that moves in a rotary manner and a piston that linearly moves forward or backward by rotation of the operating lever.
According to a method for switching rotary motion of the operating lever to linear motion, the caliper unit may be classified into various caliper units. A representative example is a ball in ramp (BIR) caliper.
The BIR caliper includes an operating ramp connected to an operating lever and rotating along with the operating lever, a corresponding ramp configured to face the operating ramp, and a ball or roller (“rotating member”) interposed between the operating ramp and the corresponding ramp. As the operating ramp rotates, the rotating member linearly moves forward or backward.
As such, the operating ramp linearly moves by the linearly moving rotating member as well, and the piston receives force from the operating ramp and moves forward or backward.
The BIR caliper further includes a high compression spring, a low compression spring, and a stopper. The high compression spring and the low compression spring are used to restore the piston to an original position, and the stopper is disposed to connect the springs in series to each other between the high compression spring and the low compression spring.
When the operating ramp moves backward in front of the stopper, the high compression spring pushes the stopper such that the piston also moves backward. The low compression spring further pushes the operating ramp backward such that the piston further moves backward as much as built in clearance (BIC). According to prior art, the piston moves backward by the high compression spring and the low compression spring that are connected in series to each other using the stopper as a medium, thereby reducing drag in a disk.
However, according to prior art, the low compression spring is easily and permanently deformed. When the low compression spring is permanently deformed, the length thereof is reduced, and accordingly the piston is not capable of moving backward as much as the BIC. In addition, as the rotating ramp reversely rotates, backward movement of the piston may be impeded. Accordingly, the brake pad does not sufficiently rotate backward to cause drag.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.